What's up with my vinyl liner?

[wbdahenry]

TFP has been an invaluable resource for me the last 12 months, and while I've not posted before, I've read A LOT and LEARNED a lot. Thanks to you all, I've had a great experience with my pool. Until this week when MYSTERIOUS wrinkles or creases in my liner appeared overnight! These don't appear to be caused by a floated liner, comparing them to other pictures found on the forum and elsewhere. There are two major creases about midway between liner seams that run the width of the pool. Pictures below:





Here's a close up:



There are a couple of other smaller creases as well. The large creases are about 1/4" to 1/2" high.

Some history may be pertinent also. The pool was installed in November of 2012. It was a warm fall in central NY, but by the time they had the liner installed, temperatures had dropped and there were wrinkles in the floor over the winter. Last spring (2013) the pool was drained and the liner reset by the pool company because of the wrinkle issues. No trouble at all last year with the liner after that, and when I opened the pool last month there were no wrinkles. We had some heavy rains last week (3 to 4 inches over two days), but still no wrinkles. Then about 2 or 3 days after the rains, I rolled the solar blanket back and these huge creases are there. I am befuddled. Can someone please help explain what may have caused this and what can I do to address it? Thanks again.

William

 

[Casey]

Welcome William. You may have ruled out ground water, but I'm not so sure as to agree with you. I believe it is caused by ground water.

 

[JamesW]

I agree with the groundwater idea. There is no set pattern of wrinkles that a liner will form when ground water causes the liner to float. Sometimes, you get a star pattern, sometimes you get linear wrinkles, sometimes something else. It depends on multiple factors such as how much groundwater, liner stretch etc

There is no easy solution. You might be able to work the wrinkles out by pushing the liner away from the wrinkle on both sides, especially when there is some ground water to reduce the pressure holding the liner down.

You might be able to lower the water level and work the wrinkle out. Just don't take out too much water or the liner could float even more out of place and make things worse.

 

[wbdahenry]

Where does groundwater come in under the liner? Through the joints of the poly panels, between the panels and the concrete floor? Will the groundwater recede of its own accord? Any other ideas about how to rectify? Thanks again for any advice or experiences you can share.

William

 

[Casey]

The ground water seeps in from the bottom of the pool. It happens usually in the Spring when we get a lot of rain and it's wet anyways. We also got a lot of snow this year so that has to be taken into acct too. Think of the ground as a sponge. There's only so much water a sponge can handle right? And it starts spilling over, anywhere it can.

You can help stop this by installing well points. They are holes dug around the pool up to 5-8ft deep. You put a large diameter PVC pipe in the hole with gravel and lower a sump pump into it and any time it fills with water, you pump it out with the pump and it eliminates the ground water coming through the bottom of the pool and shifting the liner. If you had a gunnite or fiber glass pool and you drained the pool and did NOT release the hydrostatic relief valve, you could destroy a pool in mere hours. It's been done. Just some food for thought.